The needle cage used in engines generally is incorporated in a big end of a connecting rod and mainly composed of more than one needle roller and a retainer to keep in place the needle rollers. With the needle cage incorporated in the connecting rod, the retainer keeping the rollers therein would be subjected to flexing force under a large centrifugal force exerted during revolution of a crank shaft.
The retainer while subjected to centrifugal force makes revolution to make sliding contact with an inside circumference of the big end of the connecting rod. To cope with this, the outside circular surface of the retainer generally is applied with any plated layer such as cupper-plated layer, silver-plated layer and so on.
A tester to apply a centrifugal force to a bearing specimen has been developed and disclosed in, for example, Published Unexamined senior Patent Application in Japan No. H04-24 531. The prior tester is one of centrifugal load bearing testers and envisaged to carry out duration test of the retainer under lubrication conditions of mainly two-stroke-cycle engine. Especially, this tester is developed for a needle cage which is incorporated between the big end of the connecting rod and the crank pin in the engine. The tester is envisaged for the bearing which is subjected to a large centrifugal force caused by both spinning on its axis and revolution. This tester is designed to make sliding contact with the outside circumference of the retainer of the needle cage to carry out evaluation of an anti-frictional performance.
Another example of conventional tester for roller bearings is disclosed in Published Unexamined Patent Application in Japan No. 2005-91 212, in which the lifetime test of durability of the cylindrical roller bearing is carried out by application of an edge load on a rolling contact area. With the prior roller bearing tester constructed as stated earlier, a rotating shaft is born rotationally at opposite ends thereof respectively by means of support bearings which are made of a pair of automatic aligning roller bearings. A specimen of cylindrical roller bearing is prepared between an inside circular surface of the movable housing lying around an intermediate area of the rotating shaft and an outside circular surface of the intermediate area of the rotating shaft. With the rolling bearing tester constructed as stated earlier, the center axis of the movable housing and the center axis of the rotating shaft are brought into in alignment with each other by means of the first adjusting screws and second adjusting screws each of which is prepared in pairs. With the construction as stated earlier, the radial load applied on the cylindrical roller bearing by means of the pressure device is determined with accuracy so as to prevent occurrence of the edge load to carry out the lifetime test of duration of the cylindrical roller bearing.
A further another example of prior lifetime tester for the radial roller bearing is disclosed in Published Unexamined Patent Application in Japan No. 2014-202 639, in which the stationary housing is made sufficiently higher in rigidity to carry out the reliable lifetime test for the bearing. The radial rolling bearing tester constructed as stated earlier is intended to carry out the lifetime test of the bearing. The tester for the radial roller bearing is made of the stationary housing which is made of carbon steel blank which has been subjected to forging and cutting processes.
The stationary housing as a whole is made in an integral construction inside which there is provided a lubricant sump having a cylindrical concaved bottom which is made to have an axis concentric with the central axis of the rotating shaft.
Another example of prior lifetime evaluation device for radial roller bearing is disclosed in Published Unexamined Patent Application in Japan No. H11-64 167. The lifetime evaluation device for radial roller bearing is preferred to carry out the lifetime evaluation with accuracy under the situations closer to conditions of regular usage. With the prior lifetime evaluation device for radial roller bearing constructed as stated earlier, a specimen of the test bearing interposed between rotating members of the bearing tester is stored in a casing which is raised upward by means of a compression coiled spring.
The casing having stored the test bearing therein is connected at the lower end thereof to a linkage member having a load cell. A load cylinder at the tip end thereof is pivoted to the lower end of the linkage member. Thus, variation in radial load is exerted on the test bearing by means of the load cylinder and the variable load is generated by selection in number of the rotating eccentric weight screws. With the lifetime evaluation device constructed as stated earlier, the radial load may be applied arbitrary to vary the load. Moreover, zero adjustment of the load cell may be performed the life evaluation with high precision at the condition closer to the practical use.
With the wear-proof test for the retainer in radial load tester, generally, the retainer is fastened to the rotating shaft of the radial load tester to make one revolution together with the rotating shaft to be subjected to the test load. When the retainer experiences no flex as incorporated in the engine, the retainer will be urged across a very small area against an outside ring and therefore the outside circumference of the retainer is subject to a higher contact pressure than in the engine. As a result, the surface treatment skin has torn off and thereafter the wear-proof test couldn't be executed according to the required engine conditions. With the testing device disclosed in the earlier recited Published Unexamined senior Patent Application in Japan No. H04-24 531, it is adversely required to make the testing device large scaled to resist large centrifugal load. To this end, it is needed to increase the revolution per second and the revolutionary velocity of the arms of supporting bracket to bear the specimen bearing. With the tester constructed as stated earlier, moreover, as a result of wear-proof test to make sliding contact with the outside circular surface of the retainer of the needle cage, it was shown that the sliding velocity of the retainer becomes higher compared with the actual engine because each ring for test bearings rolls through along the inside circular surface of the sun wheel to rotate on its own axis while revolving around sun wheel. In order to bear the large centrifugal load while reducing the sliding velocity down to the substantially same level with the actual engine, it is desired to increase the number of revolution of the main shaft while making the arm of the supporting bracket shorter in length. With tester constructed as stated earlier, application of the centrifugal load to the load bearing specimen is carried out to chiefly make durability test under the lubrication conditions of the two-cycle engines. Though large composite centrifugal force of revolution and rotation was applied to the needle cage, the retainer was free of urgency against a track surface or the inside circular surface of the sun wheel in the tester, so that the wear-proof test of the surface-treatment skin wasn't done under the conditions near the actual engine.
Large-scale alternation of the tester was very tough because requiring large-scale design alternation and risking high cost. With the conventional wear-proof test done in the radial load tester, the retainer is fastened to the rotating shaft of the tester as stated earlier and subjected to the test load while rotated integrally to make the sliding contact between the outside circular surface of the retainer and the inside circular surface of the outside test wheel. When the retainer has no flex as assembled in the engine, the retainer becomes urged at a very small area against the outside test wheel. Thus, as the result higher contact surface-pressure than in the actual engine affected against the outside surface of the retainer, the surface-treatment skin was torn off from the outside circular surface of the retainer and therefore the wear-proof test could not be made on the assumption of actual conditions of the engine.